A recent development in the field of electro-mechanics has been the miniaturization of various mechanical devices. Typical of such devices are tiny motors, gears, levers, and valves. These "micro-mechanical" devices are manufactured using integrated circuit techniques, often together with electrical control circuitry. Common applications include accelerometers, pressure sensors, and actuators. As another example, micro-mirrors can be configured for use in spatial light modulators.
Reliability has been difficult to achieve with micro-mechanical devices. A common reliability problem is sticking, which occurs when the device has a moving element that contacts another surface of the device. The moving element may become stuck against that surface, causing the device to cease to operate properly. A related problem is that repeated contact between elements can cause their surfaces to wear.
Because of the tiny dimensions of micro-mechanical devices, the cause of sticking and the effects of various attempts to solve the sticking problem are difficult to discern. A discussion of causes of "stiction" is set out in an article entitled "The Effect of Release-Etch Processing on Surface Microstructure Stiction" by Alley, Cuan, Howe, and Komvopoulos in Proceedings of the IEEE Solid State Sensor and Actuator Workshop (1992) pp. 202-207. Various causes of stiction that are discussed are solid bridging, liquid bridging, Van de Waals forces, electrostatic forces, and surface roughness.
Many attempts to solve the sticking problem have been directed to overcoming assumed adhesion forces by coating contacting surfaces with various substances, such as lubricants, during fabrication. However, these techniques are preventative rather than curative, and do not solve the problem of unsticking contacting elements once they have become stuck.
Supercritical fluids have been recognized as a means for drying micro-mechanical devices which have been rinsed in liquids, as part of their fabrication, resulting in stuck elements. A discussion of ameliorating liquid bridging by critical point (SCF) drying is set out in an article entitled "Supercritical Carbon Dioxide Drying of Microstructures" by Mulhern, Soane, and Howe in 7th International Conference on Solid State Sensors and Actuators (1993) pp. 296-299. However, these techniques are limited to post-rinse drying during fabrication.